The industrial demand for pressure-sensitive adhesives (PSAs) with significantly improved adhesion to substrates of low surface energy (LSE) has risen sharply in recent times. Substrates considered to be of low energy generally have a surface energy of less than 40 dyn/cm2, typically less than 35 dyn/cm2. Considered particularly critical are materials which as well as a low surface energy also possess rough surfaces and, furthermore, low Shore A hardnesses of less than 50, typically less than 40. In view of the continually improving properties and the relatively low costs, such materials are being used to ever-increasing extent in industrial applications, meaning that the demand for suitable PSAs is growing as well.
It will be desirable if such PSAs also had good properties in terms of adhesion or peel adhesion, tack, and cohesion. To date, however, it has not been possible to adjust these parameters independently of one another.
For example, block copolymer adhesives can generally be adjusted using tackifiers in such a way that high peel resistances are achieved on LSE substrates. Nevertheless, block copolymer adhesives generally exhibit poor temperature stability, since the hard domains soften at high temperatures.
Acrylate PSAs can generally be adjusted such that a high static shear resistance at elevated temperatures is achieved. In general, however, they possess low peel adhesion to LSE surfaces. Tackified, acrylate-based adhesives, such as those set out in U.S. Pat. No. 5,602,221 (Bennett et al.), exhibit improved adhesion to LSE substrates.
The proportion of the resins is limited, however, since the apolar acrylate comonomers raise the glass transition temperature Tg of the overall adhesive formulation. Through addition of tackifying resins, there is a further rise in the glass transition temperature, meaning that the tack is lost and the flow-on of the adhesive is impaired.
It is an object of the invention, therefore, to provide a PSA having improved properties. Further objects are to specify a production method for such a PSA, an adhesive tape comprising the PSA, a production method for the adhesive tape, a use of the PSA, and the use of monomers.